ABSTRACT: The body surface temperatures of the Eurasian otter Lutra lutra and the tropical giant otter Pteronura brasiliensis were studied based on detailed infrared thermography. The Eurasian otter mainly used its feet to dissipate excess heat, whereas the giant otter lost more heat from the whole body and tail. In both species, the temperature at the surface of the feet tended to decrease to a temperature similar to that of the water when the animal was submerged. The same was observed for the tail of the giant otter, and of the Eurasian otter during winter. In the Eurasian otter, temperatures of the air layer trapped within the fur were >10°C above the temperature of the ambient air or water. A specific heating of sensory organs on the head could be observed.